For this project I started from a Nerio Neri Book "Antenne. Progettazione e Costruzione - Vol. 2" (Antennas. Design and Building - Vol. 2). The book describes the building of a HF three bands (10-15-20) aluminium delta loop, but I limited the design to 20m band only.
As I use to do, I started with a MMANA-GAL model (you can find the file below).

The details of project are as follows:

- Material: aluminum tube;
- Working Frequency: 14,200 Mhz;
- Boom Length: 3.5 m/10 ft (4m/3,3ft is recommended);
- Grounded Elements.

• Radiator dimensions

- Oblique elements: 7.22m - tapering sections: 2.0m-1.8m-1.8m-1.62m with scaled diameters: 30mm-25mm-20mm-16mm
- Horizontal section 7.22m - wire 3 mmq

• Reflector dimensions

- Oblique elements 7:43 - tapering sections: 2.2m-1.8m-1.8m-1.63m with scaled diameters of 30mm-25mm-20mm-16mm -
- Horizontal section 7:43 - wire 3 mmq

For the tuning system I used a classic stub configuration but to make things easier I used a variable capacitor instead of the classic RG-8 central stub wire. This kind of tuning is better shown in the web site: http://www.omconcept.fr/delta-loop/le-condensateur.php.

Here are the simulation results and the MMANA file.